Plumb Me Puzzled...leaks there than it's not.

[stlsmiln]

Here's the situation that's got me so puzzled...

The construction is a barn-to-house conversion that my grandfather remodeled about 25-30 years ago (slab on grade). And I'm not saying he "cuts corners," but at the same time he will look for the most "economical" way of doing things every time. Pipes are copper and PVC (that we can see).

Anyway, about 2 weeks ago we noticed the carpet in the bathroom wet (thought it was left over from a shower) but within two days we were ripping up the carpet/padding and shop-vac-ing about 10+ gallons of water a day. The water comes up through a whole in the concrete where the plumbing enters for the bathtub. Believed that it was coming from a problem below the slab. Finally got a plumber out by day 3 (Friday) who took one look at it and said they'd have to send a higher-up out...who didn't get back until day 6 (Monday).

The boss looked at it, first recommended we abandon the main line under the slab and run a new line from before the house, and through the attic. After discussion, we decided that they would come back with a jackhammer once we had demoed the tub and cabinets and find the problem under the slab.

Two days later, after more than a week of flooding and having done NOTHING, the water inexplicably stopped coming through the slab. Anyone have an idea about what could cause this, liklihood that it will return, what the...?????

[phishfood]

Off of the top of my head, the most likely reason that you don't see water coming up through the slab anymore is that the water has found an easier way of escaping, probably by percolating into the dirt. The least likely reason is that the piping has mysteriously stopped leaking. You need to follow through with finding and fixing the leak, as it is likely washing a nice sized hole under your house as we speak.

Minor mistakes in installation can play a large part in how long both copper and PVC piping will last. But after 20+ years, even properly installed piping can and does fail.

[havasu]

The comment I posted awhile back seems to also fit this thread, so I'm posting it here, to tell others the concern of under-slab plumbing.

Since my problem has already been repaired, I really don't need an answer as much as I want to vent. You see, I recently had my vacation home repiped in PEX. While testing the plumbing under pressure, the contractor found that I had a pretty serious leak somewhere in my irrigation line. After hours of tracking down and isolating lines, he discovered that a 3/4" PVC tee fitting had cracked. This PVC fitting was 30" down, directly in the center of my backyard patio slab. To avoid a botch patch job, I authorized him to jack the entire concrete slab out, fix the problem correctly, and repour the concrete. He is adding french drainage and some other trick stuff, but he had to remove my firepit and I won't be replacing it.

OK, I've vented. Please never use PVC and bury it under a slab. That is just stupid! I will post pics when I take my next trip to Lake Havasu.